Hi Piyush!

As per the CBSE norms,  a student must separately pass theroy and practical examination. If you don't attend practical exam, you'll be declared Fail in Practical of subject concerned. So, you will be marked fail in the practical exam of the subject in the 12th scoresheet/report card and it will be hard for you to scored good marks in IT. Overall, you will be declared in that subject even if you get 100% marks in theory paper if you do not give practical.

Thankyou!